Method of producing polyurethane elastomer staple fibre



United States Patent US. Cl. 264-184 Claims ABSTRACT OF THE DISCLOSURE Polyurethane elastomer staple fibre free from adhesion between the onmofilament yarns is produced by dissolving a polyurethane elastomer obtained from a polyester diol or a polyether diol in a solvent of dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, or tetrahydrofuran, wet spinning the resulting solution into methanol, ethanol or propanol, drawing the resulting filaments and cutting the filaments to predetermined length.

The present invention relates to a method of producing polyurethane elastomer staple fibre which is set to a low elongation.

Specifically, the invention provides a method of producing polyurethane elastomer staple fibre set to a low elongation, which is free from adhesion among monofilament yarns, characterized in that a spinning solution is prepared by dissolving a polyurethane elastomer in dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane or tetrahydrofuran, or solvent composed essentially of any of these compounds, the spinning solution is subjected to wet spinning into one or more lower aliphatic alcohols selected from the group consisting of methanol, ethanol and propanol or solution composed essentially of one or more of such alcohols as the coagulating bath or as the second or subsequent spinning bath, the filaments thus formed out of the coagulating bath are drawn either in a state containing the solvent or after drying, to such an extent that the filaments attain an elongation at breakage of 150% or less, and thereafter the filaments are cut to a predetermined length.

Heretofore polyurethane elastomer fibres have been produced by wet spinning of a solution of an elastomer in dimethylformamide or the like into a water bath or by dry spinning of such a solution in hot gas. The filaments thus produced form, so called adhered multifilament because of great adhesiveness of the monofilaments. To overcome this, attempts have been .made, for example by the addition of talc or the like, but none of them has succeeeded in solving the problem perfectly.

As the manufacture of polyurethane elastomer fibres, it has been known that monofilaments are obtained by spinning a prepolymer of a molecular weight of about 1,000 to 3,000 containing an isocyanate group in the end directly through a diamine-water bath or the like. It has also been known that, in the above method, alcohol is added to the diamine-water bath. Nevertheless, the conventional method fails to obtain non-adhesive multifilaments for the manufacture of staple fibre.

Moreover, the fibres produced by the conventional method has elastic elongations of several hundreds of percent, and cannot be formed into blended yarn through usual blending process with a carding machine, roving process and spinning process which are applicable to ordinary fibres, e.g. cotton, viscose staple fibre, vinylon, and polyester. Only the use of special draft cut system spinning frames such as pacific converter has achieved limited success.

In an effort to cope with the above difiiculties, we

have found that, in wet spinning of polyurethane elastomer, a suitable combination of solvent and coagulating bath (or spinning bath) can prevent adhesion among monofilaments and can set the filaments to an elongation of not more than 150%. As the result, we have successfully manufactured polyurethane elastomer fibres which are capable of the being mix spun by carding machine in the usual manner.

Furthermore, the fibres produced in accordance with the present invention are not only contributory to the improvement of elastic recovery of spun yarn but are also capable of giving stretch yarns, particularly blended stretch yarns having unique texture and properties not possessed by ordinary polyurethane elastomers. Also, bulky yarns, and stretchable bulky yarns in particular, can be obtained by heat setting blended yarn containing a fibre produced according to the invention thereby causing shrinkage of the yarn and then recovering high elasticity of the polyurethane elastomer fibre which is thus set to a low elongation.

In addition, the fibre obtained by the method of the invention can have either a temporarily or permanently set elongation depending upon the drawing set condition. The fibre in which the elongation is permanently set in accordance with the invention possesses properties which fall under a category entirely diiferent from those of conventional fibres in that it has a tenacity of about 3 g./d. and an elongation of about both midway the values of ordinary rubber elastic fibre and ordinary non-elastic fibre and yet retains an elastic recovery rate which is almost complete and as high as that of rubber elastic fibre. Thus, the staple produced in accordance with the present invention exhibits outstanding properties as such and can give blended yarn having quite unique texture and other features.

On the other hand, the fibre which is temporarily set in elongation according to the invention is capable of being subjected to carding, roving and spinning processes, and develops interesting behaviours, by which it can recover the high elongation and elasticity upon heat setting following spinning.

According to the present invention, the drawing-set and adhesion-preventive effects are attained by dissolving a polyurethane elastomer in a certain solvent to prepare a spinning solution and then wet spinning said spinning solution into a certain lower aliphatic alcohol.

The combination of the solvent for the spinning solution and that for the spinning bath is most essential for the drawing-set and adhesion-preventive effects, and the use of a lower aliphatic alcohol for the spinning bath in accordance with the present invention is particularly beneficial in case of the coagulating bath and final bath. The alcohol content in the bath is preferably more than 50%.

Drawing may be carried out in an atmosphere such as air or in silicon oil. For the purpose of low elongation set, usually heat setting is required after the drawing. Usually heating at a temperature between 50 C. and the melting point or decomposing point of the drawn fibre for not more than several minutes will give the fibre a temporary set, and heating within the above temperature range for a period of more than several minutes but less than 30 minutes will give it a permanent set. Heating for a period in excess of the above limits will again give a high elongation to the fibre and will make it finer proportionally.

Particular preferred is drawing of the fibre while it still contains the solvent. Low elongation is advantageously attained at a relatively low temperature and without any special setting treatment following the drawing. Actually, it is desirable that the drawing is accomplished in the second or subsequent bath or in air by roller.

Temperature, duration, and other conditions cannot be definitely specified because they are dependent upon the solvent contents in the spinning solution and in the spinning bath. In general, however, a temperature below 100 C. and a period of several seconds to several minutes, or far milder conditions than those immediately after drying may be used.

If necessary, the fibre may be again heat set after the drawing, but usually a sufficiently low elongation set is achieved without such additional heat setting treatment. Usually suitable drawing ratio is above 50% and below the elongation at breakage or usually below 500%. To give an elongation of not more than 150% to the elastic fibre by the foregoing treatment is a prerequisite for the subsequent steps according to the invention.

Although the degree of low elongation depends on the particular composition of the polyurethane and on the drawing ratio employed, an elongation as low as 50% is attained in some cases. A fibre with such a low elongation should fall under the category of so-called nonelastic fibres but the fibre nevertheless possesses far greater elastic recovery than non-elastic ones. For this reason it must be regarded as an entirely novel fibre.

The polyurethane elastomers for use in the present invention are obtained from a polymer diol selected from the group consisting of polyester diol and polyether diol having a molecular weight of 200 to 8,000, diisocyanate and low molecular weight diol.

Suitable polymer diol is polypropylene glycol, polyethylene propylene glycol, polytetramethylene glycol, polyethylene adipate, polyethylene propylene adipate, polybutylene adipate, polyethylene butylene adipate, polybutylene sebacate, polycaprolactam, caprolactam-propylene oxide copolymer, or the like. Useful diisocyanate include aromatic diisocyanates, such as p,p'-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate, meta or para xylene diisocyanate and aliphatic diisocyanates such as hexamethylene diisocyanate.

Suitable solvent for the spinning solution is dimethylformamide, dimethylacetamide, dimethyl-sulfoxide, dioxane and tetrahydrofuran, or solvent composed essentially of any of these compounds, the content being preferably over 50%.

Usually the concentration of a polyurethane elastomer in the spinning solution is preferably more than 5% and less than 30%.

The present invention is illustrated by the following specific examples, although it is not intended that the examples restrict the scope of the invention.

EXAMPLE 1 A polyester having both terminal hydroxyl groups of a molecular weight of 1,970, which was a condensation product of a mixture of ethylene glycol and propylene glycol at a molar ratio of 80:20 and adipic acid, p,p'-di phenylmethane diisocyanate, and ethylene glycol at a molar ratio of 1:5 :4 were polymerized with heat to obtain a polyurethane elastomer (with an intrinsic viscosity of 1.10 dl./ g. in dimethylformamide at 30 C.).

The elastomer thus obtained was dissolved in dimethylformamide of 4 times the amount of the elastomer to prepare a spinning solution. The solution at a temperature of 40 C. was upon through a nozzle having 100 holes each 0.08 mm. in diameter, into isopropanol at 30 C. The spinning baths, from the first to the fourth, all were composed of isopropanol. With a spinning velocity of m./min. and a take-up velocity of 40 m./min., the filaments were drawn in the second and third baths to a total drawing ratio of 300%. After drying, the filaments were completely divided into a monofilaments, which were set to a low elongation and had a monofilament fineness of 3 d., tenacity of 9.3 g./d., and elongation of 105%. (By contrast, a sample obtained from the first bath for comparison purpose exhibited typical properties of elastic 4 fibre, and had a fineness of 12 d., tenacity of 0.8 g./d., and elongation of 450%).

After drawing and drying, the filaments were cut to length of 89 mm., which were blended with polyester filaments (8 d., 89 mm. length) at a ratio of 1:9, in the usual manner by carding machine. The sliver thus formed was spun by a worsted spinning frame into a blended yarn of a worsted count of 30s and a number of twist of 15 turns per inch. The elastic recovery of the blended yarn was better than the spun yarn solely of polyester fibre. Upon treatment in hot water at 100 C. for 15 minutes, the yarn shrank by 30%, and after drying it became stretchable bulky yarn. On the other hand, a sample directly obtained from the first bath in the same manner as above without drawing, could not be blended with the polyester fibre by the card. Also, when the spinning solution as used in this example was spun through a 50% aqueous solution of dimethylformamide, the 100 filaments were completely adhered to one another into the form of a single monofilament. Of course no staple could be obtained.

EXAMPLE 2 A polyurethane elastomer (with an N content of 4.8% and an intrinsic viscosity of 1.18 dl./ g.) which was composed of polypropylene glycol having a molecular weight of 800, p-xylene diisocyanate, and ethylene glycol, was dissolved in a mixed solvent of 15% methyl isobutyl ketone and dimethylformamide, to a concentration of 15 The spinning solution thus prepared was subjected to wet spinning and drawing and the resulting filaments were cut to length of 45 mm. in the same manner as described in Example 1.

The staple thus obtained had a fineness of 3.8 d., tenacity of 4.1 g./d., and elongation of 62%. It could be easily blended with Vinylon fibre (3 d., 45 mm. length) by carding machine in the usual manner and could be mix spun on a spinning frame.

EXAMPLE 3 A polyurethane elastomer (with an N content of 4.0%) composed of polybutylene adipate, p,p'-diphenylmethane diisocyanate, and 1,4-butane diol was dissolved in tetrahydrofuran to a concentration of 20%. The spinning solution thus prepared was spun into isopropanol containing both tetrahydrofuran and water.

The filaments formed, upon drawing to 350% and heat setting at 150 C. for 10 minutes, had a fineness of 5 d., tenacity of 2.5 g./d., and elongation of 110%. These filaments had a permanent set without any shrinkage after a treatment with hot water at C. for 15 minutes and were cut to length of 89 mm. The cut filaments could be spun with acrylic fibre in the same way as in Examp e 1. The blended yarn thus obtained had unique texture and exhibited very good elastic recovery.

EXAMPLE 4 A polyester having both terminal hydroxyl groups of a molecular weight of about 2,000 which was comprised of three components, i.e. a mixture of ethylene glycol and propylene glycol at a molar ratio of 9:1 and adipic acid, p,p'-diphenylmethane diisocyanate, and ethylene glycol were mixed at a molar ratio of 1:5:4. With the addition of 66% by weight of methyl isobutyl ketone as a solvent, the Whole mixture was heated in a Welner crusher at 100 C. for 2 hours to obtain a powdery polyurethane elastomer (with an intrinsic viscosity of 1.0 dl./g. in dimethylformamide at 30 C.) in hot condition.

After removal of methyl isobutyl ketone by cooling under reduced pressure, the elastomer was dissolved in dimethylformamide of 4 times of the amount of the elastomer to prepare a spinning solution. The solution at a temperature of 40 C. was spun through a nozzle having 100 holes each 0.08 mm. in diameter into isopropanol at a spinning velocity of 10 rn./min.

All of the spinning baths, from first to the fourth, were consisted of isopropanol. After drying, the yarn was drawn in air bath at 100 C. to a total drawing ratio of 500%.

The yarn was completely divided into monofilaments, which were set to a low elongation and had a monofilament fineness of 1.8 d., tenacity of 3.2 g./d., and elongation of 59%. (By contrast, a sample obtained from the first bath for comparison purpose exhibited typical properties of elastic fibre, with a fineness of 8.0 d., tenacity of 0.7 g./d., and elongation of 500%.)

Following the hot drawing and drying, the yarn was cut to length of 51 mm., blended with polyester fibre (2.0 d., 51 mm. length) at a ratio of 15:85 by carding machine in the usual manner, slivered by drawing frame, and spun by a worsted spinning frame to a blended yarn of a worsted count of 30s and a number of twist of 12 turns per inch. When treated in hot water at 100 C. for 30 minutes, it shrank by 48% and gave a highly elastic bulky yarn, By contrast, a sample not subjected to hot drawing was incapable of being blended with polyester fibre by carding machine because it involved various difiiculties, for example sitcking to cards and formation of nips as it was cut off.

What We claim is:

1. A method of producing polyurethane elastomer staple fibre set to a low elongation, which is free from adhesion among the monofilament yarns, comprising the steps of: preparing a spinning solution by dissolving a polyurethane elastomer obtained from a polymer diol selected from the group consisting of polyester diol and polyether diol, a diisocyanate and low molecular Weight diol in a solvent composed essentially of at least one compound selected from the group consisting of dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane and tetrahydrofuran; wet spinning said solution into a solution composed essentially of at least one aliphatic alcohol selected from the group consisting of methanol, ethanol and propanol; drawing the resulting filaments until the filaments attain an elongation at breakage of less than 150%; and then cutting the filaments to predetermined length.

2. A method according to claim 1, which comprises the steps of preparing a spinning solution by dissolving a polyurethane elastomer in dimethylsulfoxide, Wet spinning said solution through a spinneret into a solution composed essentially of at least one aliphatic alcohol selected from the group consisting of methanol, ethanol and propanol, drawing the resulting filaments until the filaments attain an elongation at breakage of less than 150%, and then cutting the filaments to predetermined length.

3. A method according to claim 1, which comprises the steps of preparing a spinning solution by dissolving a polyurethane elastomer in dimethylacetamide, 'wet spinning said solution through a spinneret into a solution composed essentially of at least one aliphatic alcohol selected from the group consisting of methanol, ethanol and propanol, drawing the resulting filaments until the filaments attain an elongation at breakage of less than and then cutting the filaments to predetermined length.

4. A method according to claim 1, wherein the coagulating bath and other subsequent spinning bath each consist of a solution composed essentially of at least one aliphatic alcohol selected from the group consisting of methanol, ethanol and propanol.

5. A method of producing polyurethane elastomer staple fibre set to a low elongation, which is free from adhesion among the monofilament yarns, comprising the steps of: preparing a spinning solution by dissolving a polyurethane elastomer obtained from a polyester diol obtained from ethylene glycol, propylene glycol and adipic acid, and p,p-diphenylmethane diisocyanate, and ethylene glycol, in dimethylformamide; wet spinning said solution into isopropanol; drawing the resulting filaments until the filaments attain an elongation at breakage of less than 150%; and then cutting the filaments to predetermined length.

References Cited UNITED STATES PATENTS 2,929,804 3/ 1960 Stenter.

3,111,369 11/1963 Gregg et al.

3,136,830 6/1964 Oertel et al.

3,336,428 8/1967 Walters 264184 X 3,365,412 1/1968 Thoma 264-184 X 3,377,308 4/1968 Oertel et al.

3,379,683 4/1968 Booth 264-184 X 3,039,895 6/1962 Yak 117138.8 3,102,323 9/1963 Adams 8130.1 X 3,140,957 7/ 1964 Tanabe et al l176 3,296,063 1/1967 Chandler l61-175 FOREIGN PATENTS 1,441,388 4/1966 France. 1,422,131 11/ 1965 France.

JULIUS FROME, Primary Examiner I. H. WOO, Assistant Examiner US. Cl. X.R. 264-436, 203 

